This invention relates to a catalytic halogenation process. More specifically, it relates to specific catalysts for use in the oxyhalogenation and disproportionation of halogenated hydrocarbons.
Ethylene dichloride (1,2-dichloroethane) is useful in that it may be dehydrohalogenated to vinyl chloride (chloroethene). Ethylene dichloride has been prepared in the past by the chlorination of ethylene using molecular chlorine and by the catalytic oxychlorination of ethylene. Several oxychlorination catalysts are known. For example, U.S. Pat. No. 3,892,816 describes the catalytic oxychlorination of ethylene by contacting ethylene, hydrogen chloride and molecular oxygen at a temperature of from about 450.degree. F. to about 670.degree. F. in the presence of a supported, stabilized cupric chloride catalyst. U.S. Pat. No. 3,634,330 discloses an oxychlorination catalyst composed of mixtures of cupric chloride and at least one alkali metal chloride or alkaline earth metal chloride supported on spheroidal particles formed mainly of hydrated silica but including certain metal oxides.
It is generally known that saturated compounds may be oxyhalogenated. A primary drawback of known processes for the oxyhalogenation of saturated compounds is their inability to selectively produce compounds which are less than fully halogenated. Thus, an attempt to produce dichloroethane from saturated compounds via known oxychlorination processes typically results in a product mixture which contains a full spectrum of chlorinated compounds which typically are fairly difficult to separate. Another drawback of said oxychlorination processes is their high operating temperatures. Additionally, a high temperature process is typically more expensive to operate than a process operated at a lower temperature. High temperatures are conducive to the cracking of ethylene dichloride to produce vinyl chloride and other more highly chlorinated compounds in the product. For example, U.S. Pat. No. 4,226,812 discloses a process wherein ethylene is oxychlorinated to ethylene dichloride, with coproduction of major amount of vinyl chloride via thermal cracking, at temperatures ranging from 350.degree. to 525.degree. C. using a catalyst consisting essentially of a mixture of copper chloride and an alkali metal chloride irreversibly melt-occluded in a molecular sieve. The process also produces chlorotrifluoroethylene from 1,1,2-trichloro-1,2,2-trifluoroethane in low conversion.
It would be advantageous to have a process for the production of ethylene dichloride which could use ethane as a starting material, as ethane has a lower energy input than ethylene. It also would be advantageous to have a process for the production of ethylene dichloride from saturated compounds which could be operated at a lower temperature than conventional processes for the oxychlorination of saturated compounds, and, perhaps more importantly, which could produce ethylene dichloride with very high selectivity. Additionally, it would be advantageous to have a process which could coproduce ethylene dichloride and ethylene. The ability to produce ethylene as a coproduct would be a further utility since the coproduced ethylene could be chlorinated using molecular chlorine to achieve an overall balanced process for vinyl chloride production.
Known oxychlorination catalysts are not capable of selectively producing ethylene dichloride from ethyl chloride (chloroethane). Nore are said catalysts capable of selectively converting ethyl chloride to ethylene and ethylene dichloride. The catalysts employed in the patents cited hereinabove all are copper-containing catalysts for the conversion of ethylene to ethylene dichloride or vinyl chloride.
U.S. Pat. No. 3,926,847 discloses a catalyst containing a polyvalent metal halide on a support which contains a synthetic aluminosilicate of mixed layer crystal structure with randomly alternating layers of montmorillonite-like and mica-like structure. The support optionally contains a synthetic crystalline zeolitic component. Said catalyst produces a "larger mole ratio of the highly chlorinated reaction products containing no hydrogen to the partially chlorinated reaction products." Thus, the catalyst is not disclosed to be capable of selectively producing ethylene dichloride and ethylene from ethyl chloride.
U.S. Pat. No. 3,987,118 discloses a process for the oxychlorination of ethane by reacting, e.g., ethane, oxygen and hydrogen chloride while in the presence of a synthetic faujasite Y zeolite ion-exchanged with copper. The process produces a mixture of chlorinated compounds including 1,2-dichloroethylene, 1,1-dichloroethane, ethylene dichloride, trichloroethylene, vinyl chloride, and perchloroethylene.
U.S. Pat. No. 3,989,806 discloses a process for the oxidative destruction of chlorinated compounds in order to recover the chlorine value therefrom by reacting a chlorocarbon feed stream with oxygen at a temperature below 500.degree. C. in the presence of at least one transition metal-containing supported catalyst. The preferred catalyst is a copper-exchanged zeolite.
U.S. Pat. No. 4,170,571 discloses a catalyst prepared by thoroughly ion-exchanging copper ions into zeolites of the ZSM-5 type. The catalyst is specifically designed to catalyze the complete combustion of hydrocarbons. Thus, it would be unsuitable for the selective production of ethylene dichloride and ethylene from ethyl chloride.
U.S. Pat. No. 4,167,528 discloses a cupric bromide catalyst on a zeolite support having a nominal pore size of about 10 angstroms. The catalyst is specifically suited to the production of tetrabromoethylene from butane.
Thus, many copper-containing catalysts are known, but none are known for the selective production of ethylene dichloride and ethylene from ethyl chloride.
Heretofore, a highly selective, energy saving, catalytic process for the preparation of ethylene dichloride (and ethylene) from ethyl chloride has not been disclosed. Such a process would be advantageous in that ethyl chloride may be prepared from ethane. Therefore, ethylene dichloride could be produced without using ethylene as a raw material as the production of ethylene by conventional processes is a very energy intensive process.